This invention relates to an exhaust gas purifying device for a marine engine and more particularly to an improved and highly effective system for treating the exhaust gases of an engine prior to their discharge to the atmosphere.
In many types of applications for internal combustion engines, the engine exhaust gases are delivered to the atmosphere through alternate exhaust gas discharges. For example, in connection with outboard motors, it is normally the practice to discharge the exhaust gases through an underwater exhaust gas discharge when traveling at high speeds. However, when traveling at lower speeds and when the high speed exhaust gas discharge is more deeply submerged, the exhaust gases are normally delivered directly to the atmosphere through an above the water exhaust gas discharge. Although such arrangements are satisfactory, if it is desired to treat the exhaust gases with a catalyzer so as to prevent the discharge of unwanted exhaust gas constituents to the atmosphere, the system for treating the exhaust gases can be extremely cumbersome.
In a conventional exhaust gas purifying device for outboard motors, a catalyst is disposed at a position in an exhaust passage connecting exhaust ports of the engine to an expansion chamber. The catalyst, however, may create a flow resistance which chokes the exhaust passage and results in decreased engine performance.
It is, therefore, a principal object of this invention to provide an improved and highly effective arrangement for treating the exhaust gases of an internal combustion engine in which the exhaust system has two different atmospheric discharges.
It is a further object of this invention to provide an improved catalyzer system for treating the exhaust gases without introducing undesirable restrictions to exhaust gas flow.